Best Place to have a Duplex Dual-Induction Carb Do

• McDonald Carb

It sounds like some of the idle passages are still plugged. On a duplex carb like yours, it sometimes helps to check the idle circuit if you pull the two 7/16" freeze plugs located just above the bowl (one is below the fuel inlet and the second is 180 deg from the first). The exposed holes are an intermediate step for the idle fuel passages and you will see an entrance and exit passage behind the freeze plug. On each side squirt some carb cleaner in each passage and see where it comes out. Some should come out the small idle holes near the throttle plates. Squirt some cleaner down the small hole next to the nozzle plug and it should come out behind the freeze plug. This will indicate any blocked passages. If they are blocked you will have to remove the small, hard stainless steel balls to be able to ream the passages. This is not easy as they are too hard to drill. Check the archives for ways to remove them. Replacement freeze plugs are available (www.robertscarbrepair.com), but you may be able to reuse the old ones. I center-drill the plug with a #21 drill (being very careful not to let the drill go in too far and mess something up) and tap 10-32, put in a screw and pull the plug with a slide hammer. This removes the plug with little damage except for the hole. Plug the freeze plug hole with JBweld, put some sealer on the edges of the freeze plug, and tap back in with a punch around the edges.

Frank